Abstract

We report on the fluid tunable transition from trapping to discrete diffraction in planar polymer waveguide arrays. A novel optofluidic polymer waveguide array platform was engineered to allow a wavelength dependent transition from a localised state where light is trapped in a defect mode to delocalised state where light is spreading through discrete diffraction. The spectral location of this transition can be controlled through a variation of the fluid’s refractive index. The platform is compatible with aqueous solutions, making it an interesting candidate for an integrated refractive index sensor to perform label-free biosensing.

Figures (7)

Operation principle: a) Increase in defect waveguide’s output power due to a change from discrete diffraction to defect trapping upon increase of fluid index, b) drop in defect output power upon a change in wavelength, c) shift of wavelength dependent transition due to change in fluid index.

a) Top view schematic of the waveguide array. The blue sections indicate 15 mm long fluid inlets to the waveguide cores. At the 3 mm long endings the cores are covered with a KMPR cladding. b) Cross-section of the shielded defect waveguide in the centre of the array and the array waveguide cores with fluid openings.

a) SEM cross-section micrograph of openings to the waveguide array cores and shielded defect in the centre. Rectangles indicate location of SU-8 waveguide cores b) close up of the defect core and c) array core.